The present invention relates, in general, to detection equipment and, in particular, to a new and useful moisture measuring device for measuring moisture of an ambient on one side of a solid wall.
Heavy oil and tar sands represent untapped resources of liquid hydrocarbons which will be produced in increasing quantities to help supplement declining production of conventional crude oil. These deposits must, however, be heated to reduce the oil viscosity before it will flow to the producing wells in economical quantities. The dominant method of heating is by injection of surface generated steam in either a continuous (steam flood) or intermittent (steam stimulation or "huff and puff") mode.
When steam is injected down long injection pipes or "strings", a significant amount of thermal energy is lost to the rock overburden (500 to 7000 feet) which covers the oil deposit. In the initial steam injection projects, the price of oil did not justify the prevention of this heat loss, but now with the price of oil at $30 or more a barrel, insulation systems for the well injection pipe become economically justified.
Several methods are known for determining the state of insulation, and specifically whether insulation used with a component has failed. Such methods include the real time or service monitoring of surface temperature using thermocouples, thermistors, thermometers, optical pyrometers or infrared cameras.
A system of monitoring the input and output fluid temperatures may also be utilized for determining the integrity of the insulation, where the component is designed for conveying a fluid. Additionally, a measurement of power output verses fuel consumption, i.e. efficiency, gives an indication of the state of the insulation since a degraded insulation would reduce efficiency.
In all of the aforementioned techniques, once the component has cooled to ambient temperature, the evidence of thermal failure is no longer present. The techniques must be exercised during real time and thus are limited to cases where real time monitoring is possible and practical.
Off-Line Thermal Testing Techniques are also known which either directly establish the integrity of the insulation or infer this integrity. The component is removed from service for testing.
According to one technique, an induced heat flow using an induction heater is monitored by an infrared camera or other temperature sensing equipment. Alternatively, the component can be placed into a test loop in which thermal efficiency is measured.
Thermal failure can be inferred in an off-line situation by observing the conditions of the component or some part thereof, which has previously been exposed to overheating. Visual inspection may determine severe degradation, for example, warping of the component due to overheating. Discoloration ot the normal surface appearance is also a clue to thermal failure.
Insulated tubing for recovery of oil from tar sands and shale, known as insulated steam injection tubing must have effective insulation to insure adequate efficiency. The tubing is used to inject steam several hundred feet into the earth's crust and reduce viscous hydrocarbons to a fluid state. It is very important to insure the thermal integrity of the tubing and prevent expensive heat loss or the costly removal and replacement of the tube string. A non-destructive method of determining thermal integrity is needed to prevent the use of defective tubes. Since defective tubes invariably acquire moisture, a small moisture detector installed within the insulating chamber would provide a quick and inexpensive quality check for each tube.
Such tubing comprises inner and outer coaxial tubes defining an annular space between the tubes which is provided with insulation means, such as thermal insulation and evacuation of the space to obtain a vacuum. The use of insulation between coaxial tubes is disclosed, for example, in U.S. Pat. No. 3,574,357 to Alexandru et al and U.S. Pat. No. 3,478,783 to Doyle.